This research project involves studies preparatory to the eventual clinical application of biventricular assist and total artificial heart (TAH). Prior to clinical use, it is necessary to identify, clarify and solve problems associated with practical clinical total heart assist and replacement including physiological, material, and surgical procedural aspects. The objectives are: 1) to separate and clarify the transient versus the permanent physiological changes in the recipient, determine causes, and find solutions, 2) investigate material problems such as calcification of pump surfaces, and control of infection (endocarditis), 3) evaluate adapting a pair of existing left ventricular assist pumps to biventricular assist or replacement. These experiments will be of 2 to 4 months duration in calves. The design of the pumps, materials of construction and experimental protocols have been established on several prior and existing research contracts and grants.